Make the UI an observer of downloads.

chrome/browser/download/chrome_download_manager_delegate.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_DOWNLOAD_CHROME_DOWNLOAD_MANAGER_DELEGATE_H_
 #define CHROME_BROWSER_DOWNLOAD_CHROME_DOWNLOAD_MANAGER_DELEGATE_H_
 
 #include "base/compiler_specific.h"
 #include "base/hash_tables.h"
 #include "base/memory/ref_counted.h"
@@ skipping 50 matching lines @@
   static void DisableSafeBrowsing(content::DownloadItem* item);
 
   void SetDownloadManager(content::DownloadManager* dm);
 
   // content::DownloadManagerDelegate
   virtual void Shutdown() OVERRIDE;
   virtual content::DownloadId GetNextId() OVERRIDE;
   virtual bool DetermineDownloadTarget(
       content::DownloadItem* item,
       const content::DownloadTargetCallback& callback) OVERRIDE;
-  virtual content::WebContents*
-      GetAlternativeWebContentsToNotifyForDownload() OVERRIDE;
   virtual bool ShouldOpenFileBasedOnExtension(
       const base::FilePath& path) OVERRIDE;
   virtual bool ShouldCompleteDownload(
       content::DownloadItem* item,
       const base::Closure& complete_callback) OVERRIDE;
   virtual bool ShouldOpenDownload(
       content::DownloadItem* item,
       const content::DownloadOpenDelayedCallback& callback) OVERRIDE;
   virtual bool GenerateFileHash() OVERRIDE;
   virtual void GetSaveDir(content::BrowserContext* browser_context,
@@ skipping 162 matching lines @@
   content::NotificationRegistrar registrar_;
 
   // The directory most recently chosen by the user in response to a Save As
   // dialog for a regular download.
   base::FilePath last_download_path_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeDownloadManagerDelegate);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_CHROME_DOWNLOAD_MANAGER_DELEGATE_H_